zeroshade commented on code in PR #14442:
URL: https://github.com/apache/arrow/pull/14442#discussion_r1000805696
##########
go/arrow/bitutil/bitmaps.go:
##########
@@ -390,15 +396,26 @@ func CopyBitmap(src []byte, srcOffset, length int, dst
[]byte, dstOffset int) {
rdr := NewBitmapWordReader(src, srcOffset, length)
wr := NewBitmapWordWriter(dst, dstOffset, length)
+ var modify func(in uint64) uint64
+ switch mode {
+ case transferCopy:
+ modify = func(in uint64) uint64 { return in }
+ case transferInvert:
+ modify = func(in uint64) uint64 { return ^in }
+ }
+
nwords := rdr.Words()
for nwords > 0 {
nwords--
- wr.PutNextWord(rdr.NextWord())
+ wr.PutNextWord(modify(rdr.NextWord()))
Review Comment:
I did a comparison on the benchmarks and it looks like you're right (looking
a bit further into the Go opimization, I don't believe they yet fully inline
functions line the `modify` case here).
I got this from the benchmarks where `old speed` is the version using an
`if` and `new speed` is using the `modify` anonymous function approach here:
```
name old speed new speed delta
CopyBitmapWithOffset/32-20 202MB/s ± 5% 201MB/s ± 4% ~
(p=0.678 n=20+20)
CopyBitmapWithOffset/128-20 566MB/s ± 3% 555MB/s ± 7% -2.07%
(p=0.033 n=20+20)
CopyBitmapWithOffset/1000-20 1.29GB/s ± 4% 1.23GB/s ± 3% -4.94%
(p=0.000 n=20+19)
CopyBitmapWithOffset/1024-20 1.31GB/s ± 3% 1.23GB/s ± 5% -6.52%
(p=0.000 n=20+20)
CopyBitmapWithOffsetBoth/32-20 174MB/s ± 3% 176MB/s ± 3% +1.19%
(p=0.028 n=20+19)
CopyBitmapWithOffsetBoth/128-20 443MB/s ± 2% 442MB/s ± 3% ~
(p=0.723 n=17+20)
CopyBitmapWithOffsetBoth/1000-20 832MB/s ± 3% 823MB/s ± 3% ~
(p=0.072 n=20+18)
CopyBitmapWithOffsetBoth/1024-20 844MB/s ± 3% 829MB/s ± 3% -1.73%
(p=0.001 n=20+20)
```
Only one case shows the function as a better option, and that's within the
margin of error, so i'll change this to being an `if` and call it a day :)
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